Oh the joy's of a comm tank......Normally things that cause stress or discomfort will increase aggression like poor water quality, etc. Maybe the house lights are to bright or they don't like the color spectrum. Just a few ideas for you, also I have used bubblers to make bubble curtains in the tank which reduces visiblity which can help too.
BTW, Your tank looks fantastic, thanks for sharing!
exactly the same happens with my comm, Richard..lights off or the light of day, it is heaven...aquarium lights on, your Aro wreaks havoc with the blacks....
that happens with my GTs tank too (wrong place and no comparison i guess but was not sure about it )
but only if i am sitting in front of the tank and looking at them (kinda like dogs do )